BMW Technical Discussions BMW related technical discussions and questions go here. |
|
Thread Tools | Display Modes |
#1
|
|||
|
|||
Top dead center for leak down test
Want to do leak downs on my 6 cyl e36. Does it matter if the cylinder is at the tdc during compression stroke or exhaust stroke?
Thanks.
__________________
Tito 82 911 SC with 3.2 73 RSR project 97 328is 99 328is 97 Lexus SC300 Manual 86 TL (gone) 993 (gone) 75 911S (gone) |
#2
|
||||
|
||||
my guess is compression as tat is what i have always done. Want to make sure both valves are closed.
__________________
Thanks! WCM (Bill) '81 911 SC Red Targa 3.6 '97 328is White Coupe (2nd Owners!) '08 335i Blue Sedan '05 Chevy Tahoe green '98 Jeep Cherokee XJ "Blue" '01 Toyota 4 Runner "Pearl" Darnestown, Maryland |
#3
|
|||
|
|||
I guess that is my question. Aren't the valves for a particular cylinder also closed at tdc for the exhaust stroke? Hence the leak down value would be the same? I guess I can try it and find out..thanks Bill.
__________________
Tito 82 911 SC with 3.2 73 RSR project 97 328is 99 328is 97 Lexus SC300 Manual 86 TL (gone) 993 (gone) 75 911S (gone) |
#4
|
||||
|
||||
Google "valve overlap"
__________________
Thanks! WCM (Bill) '81 911 SC Red Targa 3.6 '97 328is White Coupe (2nd Owners!) '08 335i Blue Sedan '05 Chevy Tahoe green '98 Jeep Cherokee XJ "Blue" '01 Toyota 4 Runner "Pearl" Darnestown, Maryland |
#5
|
|||
|
|||
thanks Bill...i will do that...
__________________
Tito 82 911 SC with 3.2 73 RSR project 97 328is 99 328is 97 Lexus SC300 Manual 86 TL (gone) 993 (gone) 75 911S (gone) |
#6
|
||||
|
||||
Valves closed, piston at the top. Find wherever that occurs and you are good If you are going through the effort, measure the piston travel with a dowel/whatever and watch the valves.
__________________
78 SC, the 'Red Car' |
#7
|
|||
|
|||
in the 911 i can easily tell that i am at TDC during the compression stroke because i can see the rotor as it goes around...i haven't done leakdowns on the BMW, but other than putting a straw or a dowel into the spark plug hole and waiting till it is out as far as it will go, i don't know how to tell if it is in the compression or exhaust stroke without removing valve cover gasket...i don't think the notch on the case is visible...but it would make sense to me as these are interference engines that the valves must be closed at the top position on both strokes...will give it a whack and see what i find...thanks guys...
__________________
Tito 82 911 SC with 3.2 73 RSR project 97 328is 99 328is 97 Lexus SC300 Manual 86 TL (gone) 993 (gone) 75 911S (gone) |
#8
|
||||
|
||||
Unless
ed
__________________
ed 2016 GT4 2005 Lotus Elise 1994 RX-7 R2 Last edited by Dandelion; 12-10-2018 at 02:12 PM. |
#9
|
|||
|
|||
ok...so looks like i need to do this during the compression stroke...
__________________
Tito 82 911 SC with 3.2 73 RSR project 97 328is 99 328is 97 Lexus SC300 Manual 86 TL (gone) 993 (gone) 75 911S (gone) |
#10
|
||||
|
||||
Absolutely. Must be on the compression stroke.
__________________
Chris M 1985 911 Carrera with a couple cosmetic only mods 2006 E90 330i 1999 E46 328i |
|
|